Rheostat and process of making the same



C. WIRT.

RHEOSTAT AND PROCESS OF MAKING THE SAME.

APPLICATION F|LED-MAR.23,191B.

1,371,287. Patented Mar. 15,1921.

Inventor M/Q t 72 MMQA Attorneys.

PATENT OFFICE.

CHARLES WIRT, OF PHILADELPHIA, PENNSYLVANIA.

RHEOSTAT AND PROCESS OF MAKING THE SAME.

Specification of Letters Patent. Patented D1 15 1921 7 Application filed March 23, 1918. Serial No. 224,283.

To all whom it may concern:

Be 1t known that I, CHARLES ,Win'r, a

citizen of the United States, residing at Philadelphia, county of Philadelphia, and State of Pennsylvania, have invented a certain new and useful Improvement in Rheostats and Processes of Making the Same, of which the following is a specification.

The objects of my invention are to produce a simple, cheap and efficient rheostat and one which is extremely compact and of small size in proportion to its capacity.

These and further objects will more fully appear in the following specification and accompanying drawings considered together or separately. I 1

I have illustrated one embodiment of my invention in the accompanying drawings in which like parts are designated by similar reference characters and in which,

Figure 1 is a longitudinal sectional view of my improved rheostat taken on the line ,11 of Fig. 2.

Fig. 2 is a transverse section of the same taken on the line 22 of Fig. 1.

Fig. 3 is a side elevation of a resistance unit. c

Fig. 4: is a diagrammatic View showing the method of inserting the resistance units in a shell.

Fig. 5 is a sectional'view on the line 5-5 of Fig. 4, illustrating the method of making the apparatus.

Fig. 6is a sectional view of a modified form of contact plate.

Fig. 7 is a detail plan view, on a reduced scaleof the skeleton frame of a modification.

:Fig. 8 is a. diagrammatic view of a further modification, and

Fig. 9 is a diagrammatic view of another modification.

In carrying out my invention I provide a resistance member composed of a coil of wire of the required material and cross 'section. 'This coil I prefer to make in two separate units a and b. a Each unit is composed of a coil 1 and a plurality of commutator rings or contact members 2. The contact members are of asuitable material which will offer the least possible resistance to the passage of an electric current. The contact members are preferably of sheet metal stamped to shape and each comprises a flat sheet 3 having a central, circular opening 4 and having an annular flange 5 surrounding the opening. The periphery of each contact member is provided with a plurality of radial notches 6. To the uppermost contact member of each unit a and Z) is secured a terminal 7 or 7 respectively, to each of which a binding post may be attached.

The contact members are engaged with the coil of each unit at equi-distant points on the coil by looping the wire through the notches 6, the looped portions of the wire alternately engaging the upper and lower surfaces of the plates between the notches as shown in Fig. 3.

The units assembled as described are spaced apart, and the contact members 2 of each unit are held in proper relative positions by means of a skeleton framework composed of spacing strips 8 of insulating.

contact members and the coil is so woundv that the wire engages the strips and is thereby retained in approximately circular coils. If desired the strips 8 may be provided at proper intervals with notches 9 which serve to secure the members of each unit in proper position and the units properly spaced apart. These notches may be dispensed with if desired.

The structure above described comprises a framework composed of longitudinal strips carrying two groups, each composed of a plurality of plates connected in series by a wire spiral, there being an equal num ber of turns of wire between each pair of plates, the groups having no metallic connection with. each other, and each plate having a central perforation in axial alinement with the perforations in the rest of the plates. The groups are spaced apart the desired distance on the strips.

Each of the sheets 3 is preferably provided with a plurality of perforations 3 the number and positions of the. perforations being the same in each sheet so that when the plates are in place the holes in each sheet will be in alinement with the corresponding holes in each other sheet.

The cage-like structure is now placed upon a mandrel 10 which passes through the perforations in the plates and is of such a frictional contact; The mandrel carryingv alined perforations 3".

size that it will engage the walls of the perforations, and hold the cage in position by the cage is now placed within a cylindrical casing 11. The casing is somewhat greater in diameter than that of the contact mein- .bers combined with theclength of the pro jecting portions of the terminals 7 in order that the cage may be placed within the casing. while in a position eccentric thereto.

hen, the mandrel is moved into axial alinement with the. casing the terminals will project through openings 1212 in the wall of the casing.

The'casing is now seated in a socket 13 in abase 141, the mandrel being centered in the casing by the engagement of one end thereing material composed of Portland cement,

sand-lime or other artificial stone composi- 131011 111. semiliquid form. The base is rocked or otherwise ogged during the pouring of the plastic material to gently agitate the same and cause it topenetrate to every part of theshell and completely embed the wires and every part of-each contact mem ber except those portions in contact with the mandrel and the rods.

7 Then the plastic material has become set the device is removed from the base and the mandrel and rods are removed by a longi tudinal, movement thus leaving a central cylindrical opening and a series of ventilating openings encircling the central opening through the entire length of the device.

The wallof the central bore being of the I g with in which case the resistance wire may same size throughout the diameter being that of the openings 1 in the commutator rings. The turns of the wire will be separated from each other by the'insulating ma terial and the commutator rings or contact members will be insulated from each other except through the wire;

A cap 16 having openings corresponding with the ventilating openings is placed over one end of the casing said cap having Y means for attaching the device to a switchboard or other su'pport 17.

The device above described comprises the stationary member of the rheostat, and in connection therewith l' employ a movable member 18 consisting of a body 19 ofins'ulating material and a metallic shell 20. V

The shell 20 has a plurality of spring fingers 21 and 21 at each end thereof and'the ends of each set of fingers norm'allv form a circle of a diameter greater than the diameter of the bore of the stationary member so that they will always elastically engage the wall of the bore. An operating rod 22 veloped will be in is secured to thebody and extends through the cap 16 and the switch board 17. The cap is provided with a bearing 23 for the operating rod which bearing also acts as a stop for the moving member 18 and is so proportioned that the movement of the member 18 in one direction is arrested when the fingers 21 are in engagement vwith the uppermost'contact member 2 of the group a and the fingers 21? are in contact with the uppermost member of the group b.

By dividing the resistance member into two groups and so proportioning the movable member that it contacts with both groups a verycompact rheostat is produced and both terminals of the device may be connected ,to the stationary element, and movable terminals eliminated.

The contact ends of the spring fingers 21 V and 21 are so proportioned. that'they will. I bridge the space between contiguous contact inembers2 to avoid arcing and to'preveiit interrupt ons in the circuit as the member 18 is moved relat vely to the contact membersp The flanges 5 ofthe contact members 2 7 sheet metal bent to annular form. The ma{ terial of therings is extendedtradially to form arms 5*. V The spacing. strips 8 are su ported in the ends oi": the arms and the whole is embedded in the plasticinsulating material as before described. This form of the device is desirable in rheostats of large size which may develop considerable heat.

If desiredthe arms 5 =may be dispensed will be possible to placerthe c'ommutator and resistance coil indifferent casings at any desired'distance-apart as shown in Fig. 8.

Instead of loops of the resistance coil be- 1 ing employed to connect the coil withthe rings, wires 5 of low I'GSlStZtIICQinflYbBQHlployed. By this means all oftheheatfdea structure removed from the commutator. V V

In accordance with patent statutes I have described the principle of my invention, together with the apparatus which I now consider to represent providing for a more gradual.

the provisions of the the best embodiment thereof, but I desire to have it understood that the f'apparat us shown'is merely illustrative, and that the invention maybe carried out in other ways.

Having thus described' my invention what "I now claim as new and desire to secure by Letters Patent, is: r

1. A rheostat having a resistance coil, contact members engaged by the coil, a skeleton frame of insulating material separating the contacts, and a body of molded, plastic insulating material in which the resistancecoil is embedded.

2. A rheostat having a resistance coil, contact members engaged by the coil, a skeleton frame of insulating material separating the contacts, and a body of molded, plastic insulating material in which the resistance coil and frame are embedded.

3. Arheostat having a resistance coil, contact members engaged by the coil, a skeleton frame of insulating material separating the contacts, and a body of molded, plastic insulating material in which the resistance coil, contact members and frame are embedded;

. member are embedded, said contact member having the perforation thereof'free of the insulating material.

6. A rheostat havinga resistance coil, a plurality of annular contact members engaging the coil, a skeleton frame of insulating material separating the members, and a body of molded plastic, insulating material in which the coil, contact members and frame are embedded, the bores ofthe contact members being free of the insulating material.

7. A rheostat having a plurality of resistance coils, a contact member engaging each coil, an insulating frame supporting and separating the coils, a body of molded plastic, insulating material in which the coils, frame and contacts are embedded, there being a portion of each contact member free of the insulating material, and movablle means for electrically connecting the 001 s.

8. A rheostat comprising a commutator composed of superposed rings having internal contact surfaces, a resistance coil surrounding the commutator, connections between the coil and rings, and a body of plastic insulating material surrounding the rings and coil.

9. A rheostat, comprising a plurality of superposed rings forming a tube, said rings being insulated one from the other, a resistance coil connected at intervals with the rings, and a member movable longitudinally of the tube and adapted to contact with the rings, a body of plastic, insulating material surrounding the rings.

10. A rheostat having a resistance unit comprising superposed annular contact members, a resistance coil connecting the members in series, said members being electrically separated except for the coil, a second resistance unit comprising superposed annular contact members, a resistance coil connecting the members in series, said members being electrically separated except for the coil, said units being arranged in axial alinement, a lead connected to each unit, a body of plastic insulating material surrounding the members and coils and in sulating the units from each other, there being a recess in the body in alinement with the bores, of the members, and a movable member adapted to bridge the space between the units and contact with corresponding members in each unit.

11. A rheostat having a resistance unit comprising superposed annular contact members, a. resistance co-il connecting the members in series, said members being electrically separated except for the coil, a secondresistance unit comprising superposed annular contact members, a resistance coil connecting the members in series, said members being electrically separated except for the coil, said units beingarranged in axial alinement, a lead connected to each unit, a body of plastic insulating material surrounding the members and coils and insulating the units from each other, there being a recess in the body in alinement with vthe bores of the members, and a movable member adapted to bridge the space between the units and contact with corresponding members in each unit, there being a plurality of openings in each member, said openings in different members being in alinement, there being corresponding openings in the body in alinement with the alined openings in the members.

12. A rheostat having a resistance coil, a plurality of contact members engaging the coil, said contact members each having a central perforation, said perforations being in alinement, each contact member having a series of holes, said holes being in alinement, a body of molded, plastic, insulating material embedding the contact members and coil, said body having a chamber in axial alinement with the central perforation and chambers in alinement with the holes.

13. A rheostat comprising a plurality of superposed conducting members having exposed, internal contact surfaces, a movable member having spring fingers adapted to contact with the contact surfaces, said movable member being supported in engagement with the contact member by friction only, whereby all of the friction developed will be effective for securing electrical-connection between'the movable member and superposed conducting members having eX-V conducting members, and a resistance coil *connected at intervals to the conducting i'members.

14:. A rheostat comp-rising a plurality of posed, internal contact surfaces, a movable member having springfingers-adaptod to 10 contact with thecontact surfaces, said movable member being supported in engagement with the contact member by friction only, whereby all of-the' friction developed will be effective for securing electricalconnection between I the movable member and conducting members, and a resistance coil connected at intervals to the conducting Vmembers. v 1 15. The 'method of making rheostats alined perforated plates of conducting material at intervals on strips. of insulating material, placing a mandrel in the alined I perforations, winding a coil of resistance j wire outside of the strips, engaging the wire at intervals with the plates, and removing the mandrel from thejperforations.

17. The method of making ,rheostats i which consists in forming a skeleton frame- Work of a plurality of annular plates of method of making 1 rheostats' conducting material 'spacedapart by means of strips of insulating material,':winding a co l of reslstance wire. around the framework, said wire engaging the plates, placiflllg the framework on a mandrel, sa1dman-1 drel closely engaging the bores of the plates, placing the framework. and mandrel within a shell hav ing ai diameter ,greater than the diameter ofthe framework-filling the shell between its walls and the mandreli with a body of plastic insulating material,

and removing the mandrel.

:18; The-' method of making rheostats which consists in forming a skeleton framework of a plurality ofv annular plates ofa r I conducting material spaced apartby. means of strips of insulating material, windinga coil of Y resistance wire around the framework, said wire engaging the plates, placplates, each platehaving-a seriesof holes therein, theiholes' in the plates being in alinement, placing a' 'rod' in each set vof alined holes,i plac1ng' the; framework, rods-"f;

'ing the framework'on a mandrel, said man-; .2 'drel closely engaging the. bores-v. of the V and mandrel withina shell' having a diameter greater than the diameter of the framework, filling the shell: between its walls" and the mandrel with a body 'of'plastic insulat ingmaterial, and removing the rod'siandsi-f' mandrel;

This specification signedand: witnessed this QOth-day of March, 1918; V

CHAR-LES VIE T.

Witnesses: V i ,i'

J. F. CoLnMA'N 'A: E. RENTONif 

